Question

Before the advent of solid-state electronics, vacuum tubes were
widely used in radios and other devices. A simple type of vacuum
tube known as a diode consists essentially of two electrodes within
a highly evacuated enclosure. One electrode, the cathode, is
maintained at a high temperature and emits electrons from its
surface. A potential difference of a few hundred volts is
maintained between the cathode and the other electrode, known as
the anode, with the anode at the higher potential.

Suppose a diode consists of a cylindrical cathode with a radius
of 6.200�10?2 , mounted coaxially within a cylindrical anode with a
radius of 0.5580 . The potential difference between the anode and
cathode is 350 . An electron leaves the surface of the cathode with
zero initial speed (). Find its speed when it strikes the anode. v
final= ? m/s